High-frequency amplifier means with enhanced output resistance

Abstract

The input impedance of a high-frequency monolithic integrated-circuit amplifier is modified to increase the maximum output power capability of the amplifier. This modification compensates for a reduction in output resistance at high frequencies caused by feedback capacitance coupling the output and input of the amplifier.

We claim: 
     
       1. A monolithic integrated-circuit amplifier means for operating over a predetermined range of high frequencies, said amplifier means including: a. an amplifier stage having an output resistance, an equivalent input impedance comprising an input resistance electrically connected in parallel with an input capacitance, and feedback capacitance coupling the amplifier stage output to said input impedance, said coupling, during operation in said predetermined frequency range, contributing to a voltage drop across the input impedance which brings about a decrease in said output resistance; and   b. an input-impedance-modifying stage having an output impedance coupled in parallel with the amplifier stage's input impedance, said output impedance having a magnitude which is significantly smaller than the magnitude of the input impedance, thereby significantly decreasing said voltage drop and increasing said output resistance in said predetermined frequency range.   
     
     
       2. An amplifier means as in claim 1 where the output impedance of the input-impedance-modifying stage comprises a resistive component. 
     
     
       3. An amplifier means as in claim 1 where the output impedance of the input-impedance-modifying stage includes an effective output resistance which is significantly smaller than the input resistance of the amplifier stage. 
     
     
       4. An amplifier means as in claim 1 where the output impedance of the input-impedance-modifying stage comprises a capacitive component. 
     
     
       5. An amplifier means as in claim 1 where the output impedance of the input-impedance-modifying stage includes an effective output capacitance which is significantly larger than the input capacitance of the amplifier stage. 
     
     
       6. An amplifier means as in claim 1 where the input-impedance-modifying stage comprises a resistance electrically connected in parallel with a capacitance. 
     
     
       7. An amplifier means as in claim 1 where the input-impedance-modifying stage comprises an inductance and at least one capacitance. 
     
     
       8. An amplifier means as in claim 1 where the input-impedance-modifying stage has an input impedance which is substantially equal to the output impedance of said stage. 
     
     
       9. An amplifier means as in claim 1 where the amplifier stage comprises a transistor. 
     
     
       10. An amplifier means as in claim 7 where the amplifier stage comprises a bipolar junction transistor. 
     
     
       11. An amplifier means as in claim 7 where the amplifier stage comprises a field-effect transistor. 
     
     
       12. An amplifier means as in claim 1 where the amplifier stage comprises a bipolar junction transistor and a DC current bias source coupled to a base of said transistor, and where the output impedance of the input-impedance-modifying stage includes an effective output resistance which is significantly smaller than the input resistance of the transistor. 
     
     
       13. An amplifier means as in claim 1 where the amplifier stage comprises a bipolar junction transistor and a DC current bias source coupled to a base of said transistor, and where the output impedance of the input-impedance-modifying stage includes an effective output capacitance which is significantly larger than the input capacitance of the transistor.